[Asterisk-Users] Modems supported by Asterisk

[Witold P. Krecicki]

Which modems are supported by Asterisk for full-duplex (as a VoIP-PSTN
gateway) operations? I've tried Asmax Mustang (based on TI RK 56000
chipset) but it's 4-bit only, also tried Zoltrix on Rockwell 56k
chipset, hacked a lil' bit chan_modem_aopen (so it chooses 7200Hz
instead of 8000), sound was 'understandable' but only one-way :/ .Does
anybody has experience in using full-duplex voice modem with Asterisk?
Are there any cheap alternatives? 
WK